Jocelyn Mayer wrote: > On Wed, 2007-11-07 at 19:32 +0100, Fabrice Bellard wrote: >> I noticed that some target CPUs macros have been added while they do not >> seem necessary. I don't like that because it introduces more #ifdefs >> which prevent making a version supporting simultaneously all the CPUs. >> >> In particular I saw the following: >> >> - TARGET_MIPSN32 : it is always combined with TARGET_MIPS64 in >> target-mips/. If its only usage is to select a different Linux ABI, then >> I suggest keeping TARGET_MIPS64 and using another define to choose that. >> >> - TARGET_PPC64H, TARGET_PPCEMB : I see no reason why they cannot be >> handled dynamically as the other PowerPC CPU types, provided that >> TARGET_PPC64 is defined. Is it the long term plan ? > > PowerPC embedded models are already available (should say should be as > none are actually implemented) when PPC64 is defined. But as those are > mainly PowerPC 32 with some extensions to manipulate the 64 bits GPR, > it's a great help if we can avoid doing all operations in 64 bits when > running on a 32 bits host (which would greatly decrease performances by > at least a factor of two, which is not acceptable). Then having a > specific 32 bits target using 64 bits register is very useful if one > want to use those features, but may be disabled if the host is 64 bits. > Note that most (all ?) embedded Freescale PowerPC microcontrollers > implement those extensions and that some ones are greatly interrested > with having an usable emulation avaible for those CPUs.
OK for the speed gain, but such features make the code more difficult to test because there are a lot of possible combinations. I'd say the same about the fact that ppc_gpr_t can be 64 bit long on a pure 32 bit CPU. > The PowerPC 64 with hypervisor mode support could be removed only if: > - the fact of emulating hypervisor feature do not slowdown the emulator > (which I greatly doubt, but there may be great surprises) I greatly doubt too. > - someone provide an open-source hypervisor, compatible with the ones > used on real machines, that would allow at least Linux to be able to run > on a CPU with hypervisor mode available. Most 64 bits PowerPC, including > the 970 (ie G5) have the hypervisor mode support implemented. If the > hypervisor mode emulation is present, the OS won't be allowed to access > most SPR and some exceptions will need to have some specific handlers in > the hypervisor firmware. As I don't know such a software available, the > hypervisor mode can not be enabled for "standard" PowerPC 64 emulation; > or no-one will be able to actually use the emulator, except if using the > venerable but mostly undocumented (and nearly impossible to find on real > hardware) PowerPC 620 CPU. > Furthermore, running (or emulating) a SMP machine on a 64 bits PowerPC > with hypervisor features without hypervisor software is exactly > impossible. > Then I don't see how we can do without a separated target for hypervisor > features support. What you say does not justify the separate ppc64h target : it just implies that you need to add a separate machine to make hypervisor tests. Fabrice.